Stringent environmental constraints imposed by government regulation upon the oil and gas producing industry has led to the need for new “greener' chemistries, which have less environmental impact. This environmental drive has been spearheaded by North Sea Regulators such as CEFAS, and due to their success similar programs are being implemented in other oil producing regions. Operators now demand identical levels of performance with existing treatments along with the fulfillment of the new environmental criteria for any chemicals that may be contained, for example, in rig overboard discharge.
Corrosion inhibitors are given particular attention due to their inherent design to partition into the aqueous phase. The environmental impact of a corrosion inhibitor is often defined by three criteria: biodegradation, bioaccumulation and toxicity. All three criteria have benchmarks that must be met for a chemical to be permitted for use, with different emphasis on each depending on which regulator controls the waters.
Quaternary nitrogen compounds (Quats) have been used extensively as they form a film on the surface of steel, are stable over a wide range of pH and temperature, cost effective, efficient in sour conditions and inhibit microbially induced corrosion (MIC). See, for example, U.S. Pat. Nos. 7,057,050, 6,488,868, 5,756,004 and WO 2003042428 A1. However, due to their inherent biostatic properties their biotoxicity profile is often unacceptable and the compounds are not readily biodegradable.
Accordingly, there is an ongoing need for new, effective, environmentally friendly corrosion inhibitors which meet the new regulatory criteria.